The invention concerns a twin-wire section for forming a ply of a multiply web of paper or cardboard.
German patent disclosure DE 40 31 038 A1 illustrates a twin-wire former having a twin-wire zone beginning with a first group of dewatering slats, extending then to a forming roll, with the twin-wire zone running beyond the forming roll and at the end over a suction box, once the two twin wires separate. This embodiment seeks a maximally high web moisture content at departure of the forming roll in order to achieve a high ply bond strength in the multiple web. This involves the risk that with the "jagged waterline" described in the document excessively wet stock suspension may in the peaks proceed up to the couching point and be crushed there.
U.S. Pat. No. 4,207,144 shows and describes the wet section of a paper machine with a headbox, a predewatering section following it and formed by a single wire, and then a twin-wire zone which is formed by the said wire and an outer wire enclosing said zone. This system features scrapers merely in the predewatering zone. But it does not contain any rigid dewatering slats in the one wire loop and no flexible dewatering slats either in the other wire loop.
The problem underlying the present invention is to propose a twin-wire section which avoids the occurrence of such a jagged waterline.